As a follow up to the above post, I picked up my 2000 Class C, MH 2 1/2 years ago. It came with one 12 volt house battery of unknown age.
I wanted something easy and inexpensive so I installed 2, 6 volt batteries, wired in series, into one of the storage compartments and tied them to the original, 12 volt battery.
I added a 1000 watt inverter and traveled for 2 summers, mostly in non electric state parks and Flying Js.
We could have lights, watch Sat. TV, for too many hours, run a small fan all night and use my Mr. Coffee, 2 times in the AM, before I got a low voltage warning.
The batteries could still start the generator.